Floras en las capas rojas de la cuenca permica de Lodeve (Sur de Francia).
In the Lodeve Basin, the Permian sedimentation started with fluviatile clastics and lacustrine black shales of the Usclas-Saint Privat and the Tuilieres-Loiras Formations. These sediments (formerly named "Grey Autunian") were deposited under a warm and humid climate indicated by laminated lake sediments which yielded a rich and well-known flora dominated by conifers but where callipterids show a remarkable diversity (Grand'Eury, 1877; Zeiller, 1898; Florin, 1938-1945; Doubinger, 1956). Higher up, in the transition zone of the Upper Tuilieres Loiras to Lower Viala Formations, the facies changed from grey to red and from fluvio-lacustrine to dominant fluvial. In grey sediments, the plant assemblage is equally dominated by callipterids and conifers but with the remarkable co-occurrence of calamites (Doubinger, 1963; Galtier and Broutin, 1995; indicated as macroflora B on Fig. 1, Lopez et al., 2008). From the Upper part of the Viala Formation onwards, the definitively red facies have been deposited under semi-arid conditions. Red beds of the transition zone contain a small plant assemblage which was described (Doubinger and Kruseman, 1965) at the same time, and partly confused, with the flora from the overlying Rabejac Formation. Above a major unconformity, the second sedimentation cycle (formerly named "Saxonian Group") starts with fanglomeratic deposits of the Rabejac Formation. This facies yielded a small flora (= flora C, Fig. 1, Lopez et al., 2008) with the remarkable first record of Supaia for the Lodeve Basin (Doubinger and Heyler, 1975). Deposition also took place in an alluvial/flood plain environment with periodically water-filled ponds, however, in the top of the Rabejac Formation there is a fluent transition into the playa sediments of the overlying Salagou Formation (Korner et al., 2005). The occurrence of fossil plants in all red pelites is rare and their preservation is rather mediocre. The objective of this paper is a review of the available data concerning the floras from the red beds of the Lodeve Basin. This study includes the re-investigation of plants from red beds ranging from the Transition Zone of the Tuilieres-Loiras to Viala formations up to the Rabejac Formation, presently kept in diverse collections (Universite Montpellier 2, Museum National d'Histoire naturelle Paris, Universite Lyon 1, Musee Fleury Lodeve), and the first description of plants recently collected from fossiliferous rills and other levels from the Salagou Formation (floras D-E, Fig. 1, Lopez et al., 2008).
2. Techniques and studied material
The fossil plants are preserved as impressions or casts without organic matter. They are generally more or less preserved in three dimensions. This concerns stems which kept their cylindrical volume as well as compound leaves showing pinnules lying in different planes however no anatomical detail is preserved. As a result, the degagement technique (Fairon-Demaret et al., 1999) has been used in some cases, for example to reveal the three-dimensional organisation of leaves. The general method of study is a combination of camera-lucida drawings and of photography under reflected light.
1) Specimens from the Rabejac Formation:
-"Callipteris conferta" and "C. martinsii" (figured by Doubinger and Kruseman 1965, Pl. XII, fig. 1; pl. XIII, figs 1 and 5), "Callipteris uralensis" (figured by Doubinger and Heyler 1959), Supaia sp., cf. Walchia, Taeniopteris sp., cf. Crassinervia (collections Universite Montpellier 2, referred to as UM2LOD).
-"Callipteris" sp., Supaia sp., cf. Walchia (collections Musee Fleury, Lodeve, referred to as MULOD).
- "Callipteris" cf. uralensis figured by Doubinger and Kruseman (1965, Pl. 13, fig. 2): specimen Fr. 62, coll. Universite Lyon 1.
- "Callipteris " cf. uralensis, Supaia sp. (figured by Doubinger and Heyler 1975, Pl. 1, figs. 1-3): collections Museum National Histoire Naturelle Paris, referred to as MNHNP.
2) Specimens from unspecified origin (ranging from the Tuilieres-Loiras transition zone up to the Rabejac Formation): ?? Calamites sp., Rhachiphyllum sp., Walchia sp., Taeniopteris sp. (collections in Lodeve and Montpellier).
3) Specimens from the Viala Formation: Rhachiphyllum sp. (collection Univ. Montpellier).
4) Specimens from the Salagou Formation:
-Unnamed specimens of branched stems and leaves, conifer twigs, cone, small taeniopterid leaf, collected by J. Lapeyrie from several rills at Bouisset, Dio, La Prade, Le Deves, Rieupeyre-La Boutine (see Garric, 2001).
-Dichophyllum-like specimen from Arieges, collected by J. Schneider.
-Unnamed specimens of stems and almond-like organs, collected near La Lieude by G. Gand, J. Schneider and colleagues in 2004 (all material in collections Univ. Montpellier).
3. Historical survey
3.1. Macroflora from the red beds of the Transition Zone
Doubinger (1963) first described a plant assemblage (13 taxa) from grey to yellow to red pelites exposed near the Mas d'Alary but unfortunately she did not provide any illustrations and we have not been able to locate this material. Later, Galtier and Broutin (1995) described and illustrated a similar flora from grey sediments of the same zone exposed in the former uranium mine. Both assemblages are characterized by the remarkable co-occurrence of calamites with callipterids and conifers. In contrast, the plants described by Doubinger and Kruseman (1965) from the transition zone, near St Alban and St Martin du Bosc, are preserved in red pelites. The small assemblage: "Callipteris" conferta, "C." marttinsii, "C." cf. uralensis, Schuetzia sp., Walchia sp., W. hypnoides, cf. Ullmannia, consists only of callipterids and conifers. Some have been illustrated (cf. Table 1) but all plant fossils are fragmentary, sometimes "blurred" and their identification is doubtful. The most interesting taxa are "C." martensii and "C." uralensis elsewhere known in the Late Permian of England, Germany and Russia and not occurring in underlying deposits of the Lodeve Basin.
3.2. Flora from the Viala Formation
Previous studies by Doubinger and collaborators did not record any macroflora from the red pelites of the Viala Formation. In this paper we report the rare evidence of plants from this level. Interestingly, a microflora (Odin et al., 1986) was obtained from a single bed at the base of the Upper Viala Formation and this indicated a dominance of bissacate pollens and the appearance of Lueckisporites.
3.3. Macroflora from the Rabejac Formation
Doubinger and Heyler (1959), Doubinger and Kruseman (1965), Doubinger and Heyler (1975) described plants preserved as impressions from the Rabejac Formation. The plants are difficult to identify at the specific level due to relatively poor preservation. The flora includes nine taxa, either figured or not, as listed on Table 1.
It is significant that five of these taxa ("Callipteris" conferta, "Callipteris" uralensis, "Callipteris" martinsii, Walchia sp. and Culmitzchia cf. hirmeri) have been described, at the same time by Doubinger and Kruseman (1965), as co-occurring in an underlying horizon of the "Transition Zone". Of the four remaining taxa, Ernestiodendron filiciforme occurs in the Early Permian, Usclas-Saint Privat Formation, of the same Basin whilst Pecopteris cyathea is a species both common in the Late Pennsylvanian and in the Rotliegend of Germany (Holotype from Manebach). As a result of previous studies, the Rabejac Formation is characterized by the first record of Supaia and Pseudoctenis. Unfortunately the last taxon has not been illustrated and we have not been able to find the specimen mentioned by Doubinger and Kruseman (1965). In contrast, a number of specimens assignable to Supaia have been recognized and are described in this paper along with a reconsideration of the occurrence of uncommon taxa like "Callipteris" uralensis and "Callipteris" martinsii.
4.1. Macroflora from the Rabejac Formation and underlying red beds
The plants essentially belong to callipterid pteridosperms and conifers; in addition, possible cycads and problematic specimens of calamites and ferns must be mentioned.
Previous authors did not mention any representatives of the sphenopsids in red sediments of the Lodeve Basin. A single specimen (LOD 1007, collections University of Montpellier) seems to represent the pith cast of a calamitean trunk. The specimen is 9 cm in diameter and shows one node and closely spaced verticals ribs suggestive of Calamites cistii. This specimen being of unspecified origin may be from the red beds of the "Transition Zone". This would not be surprising, considering that calamiteans have been reported from the grey sediments of the same zone by Doubinger (1963) and Galtier and Broutin (1995).
Doubinger and Kruseman (1965) described and illustrated Pecopteris cyathea and P. cyathea var. major from the Rabejac Formation, however, we have not been able to find these specimens and no other example of this fern has been recognised during our re-investigation of the collections.
Callipterids represent the majority of fossil plants preserved in the red sediments from the Rabejac Formation. Rhachiphyllum sp.
A 20 cm long compression of a frond from the Rabejac formation was attributed to "Callipteris conferta" by Doubinger and Kruseman (1965, Pl; 12, fig. 1) on the basis of the overall morphology, size and pinnule shape and despite the indistinct venation. Re-investigation of this specimen (Fig. 1) reveals a number of features (pinnae arranged at wide angles of about 90[degrees], pinnules with indistinct midvein , apparent multiple venation on the primary rachis) which are not in accordance with Autunia conferta as it has been re-defined by Kerp (1988). The three-dimensional preservation of the frond shows that along each pinna the pinnules are directed towards the abaxial side of the frond (i.e. opposite the exposed side). The pinnules are vaulted, obliquely inserted and decurrent with their tips embedded in the sediment; as a result they appear round-ovate, less than 10 mm long and 5 mm wide. Intercalary pinnules are inserted laterally on the primary rachis but do not cover its adaxial side. Due to the thickness of the lamina, the pinnule midvein is not visible whilst the pinna rachis shows only a faint midvein and the primary rachis shows several parallel and branched veins (Fig. 1). According to the re-evaluation of the classification of callipterid pteridophylls by Kerp (1988) and Kerp and Haubold (1988) we suggest to refer this type of frond to the morphogenus Rhachiphyllum Kerp. Additional material, kept in the collections of Montpellier University and collected in the Viala Formation, consists of two smaller fronds with the same habit (pinnae inserted at wide angle and small rounded pinnules). The preservation is relatively poor and does not allow a more precise taxonomic description of this type of frond.
[FIGURE 1 OMITTED]
Autunia conferta (Sternb.) Kerp
Doubinger and Kruseman (1965, pl. 12, fig.2) illustrated a pinna fragment with three pinnules clearly showing the venation characteristic of the species. This specimen, not yet located in the collections, comes from the Transition Zone where A. conferta is very common in the grey facies. However, several fragments of bipinnate fronds from the Rabejac Formation may be attributed to A. conferta despite a relatively poor preservation; they show pinnae inserted at angles of 30 to 60[degrees] and pinnules with a strong midvein (Fig. 2A).
cf. Peltaspermum martinsii (Germar) Poort and Kerp.
Two fragments of small bipinnate fronds showing small "shrivelled" pinnules have been attributed to "Callipteris martinsi" by Doubinger and Kruseman (1965, Pl. 13, figs. 1, 5) who emphasized the contrast between this species and the other associated callipterids with broad pinnules. The two figured specimens, kept in the collections of Montpellier, have been studied together with a third one of same origin (i.e. Rabejac Formation) showing only portions of pinnae. This plant is characterized by small (2.5 - 4.5 mm long, 1.5 - 2.4 mm wide), alethopteroid, entire-margined pinnules, certainly coriaceous with thick lamina and indistinct venation (Fig. 2B-C). The pinnules are more or less regularly spaced (at 3 to 4.8 mm intervals) along the pinna rachis. Pinnae are suboppositely attached to the primary rachis; they are slender, up to 70 mm long, showing a distal decrease of pinnule length (Fig. 2B). Intercalary pinnules, similar to other pinnules, are obscuring the primary rachis (Fig. 2B). The attribution of these specimens to Lepidopteris (C.) martinsii has been questioned by Kerp (2000) who suggested that they are most probably conifers. Despite relatively poor preservation, present evidence supports the interpretation of the ultimate axes as pinnae bearing alternately small pinnules rather than ultimate branches bearing spirally arranged needle-like conifer leaves. Lepidopteris is a morphogenus based on foliar morphology and the combination L. martinsii is preferred by Kerp and Haubold (1988) for such specimens. However, Peltaspermum has been redefined by Poort and Kerp (1990) as a natural genus including sterile foliage and ovuliferous organs for the species P. martinsii. The foliage from Lodeve is incomplete however the pinnae are slender and the pinnules are similar to those in specimens of Peltaspermum martinsii illustrated by Poort and Kerp (1990) and Visscher et al. (2001). The Lodeve specimens look almost identical, in pinna and pinnule organisation, to the "Callipteris martinsi" described by Stoneley (1958, fig. 5 a,d) from the Upper Permian of England, however, slightly lobed pinnules have been illustrated in one English specimen, a feature unknown in our material. Therefore, we propose that the Lodeve specimen be referred to as cf. Lepidopteris martinsii.
[FIGURE 2 OMITTED]
cf. Supaia (=Callipteris uralensis Doubinger and Heyler).
Several fragments of pinnae bearing subopposite relatively long pinnules have been first attributed to Callipteris uralensis by Doubinger and Heyler (1959), then to C. cf. uralensis by Doubinger and Kruseman (1965). They are from the Rabejac Formation with the exception of one specimen from the Transition Zone (cf. Table 1). Two specimens, kept in Montpellier, originally illustrated by Doubinger and Heyler (1959) and another kept in Lyon, illustrated by Doubinger and Kruseman (1965, Pl. 13, fig 2), have been reinvestigated as well as a dozen of specimens referable to this taxon from collections in Montpellier, Paris and Lodeve. Doubinger and Heyler (1959) emphasized the biconvex shape of the pinnules with a lamina "more or less inclined as a roof", i.e. inverted V-shaped in section with the midrib forming the top. This feature is well visible (Fig. 3A) on all the specimens but it is more pronounced in the most proximal region of the pinnule. The midvein is generally prominent and basally decurrent whilst the oblique lateral veins are very narrow and closely spaced. All the observed specimens are incomplete pinnae ranging from 4 to 26 cm long, pinna rachis being 2 to 4 mm broad, subopposite pinnules ranging from 20 to 60 mm long and 5 to 11 mm broad. This exceeds the length values (20 to 38 mm long) given by previous authors who noted the alethopteroid-type pinnules, basally confluent, and resulting in a 3-5 mm lamina fringe along the rachis. The interval between pinnule midveins ranges from 7 to 15 mm and the pinnule lamina generally overlap a little (Fig. 3A). Doubinger and Heyler (1959) justified the attribution to Callipteris uralensis by the large size of the pinnules, their decurrent base along the rachis and their "roof-shape". However, the specimens of C. uralensis figured by Zalessky (1927) and Neuburg (1948) show broad pinnules with a smaller ratio (pinnule length/width), i.e. the pinnules in the Lodeve specimens appear more slender. The venation of the pinnules is more similar to that observed in Supaia (see below) than to the type material of C. uralensis described by Zalessky. Another difference is the pronounced "roof-shaped" aspect of the pinnules in Lodeve specimens (Fig. 3A) which may be explained by a thicker lamina and the three-dimensional morphology of the pinnules preserved in a coarser-grained sediment. These specimens have thick and biconvex pinnules very similar to some of the Supaia material from the Hermit Shale described by White (1929): see for example Supaia sturdevantii or Supaia sp. (White 1929, Plate 18, fig. 2a or Plate 32, fig. 2). Moreover in some examples two pinnae lying side by side are diverging from a point that certainly represents a bifurcation of the rachis, a feature demonstrated in the fronds of Supaia that are discussed below. This may explain why Doubinger and Heyler (1975) finally questioned the possible attribution of their specimens of C. uralensis to the genus Supaia. Seven specimens in Paris and most in Montpellier are from the Rabejac Formation (Cartels locality). However, of some others the origin is unknown and we cannot exclude that they are from the red beds of the Tuilieres Loiras Formation. Considering the differences and uncertainties mentioned above, the attribution of this material to C. uralensis is very dubious. Awaiting a revision of the type material of Zalessky, C. uralensis has been classified as "Species dubiae" by Kerp and Haubold (1988). Therefore, considering the probable bifurcation of the rachis, we propose to follow Doubinger and Heyler (1975) final questioning and to designate these callipterid specimens from the Tuilieres-Loiras and Rabejac Formations as cf. Supaia instead of Callipteris cf. uralensis.
Supaia sp., aff. thinnfeldioides.
The first report of the genus Supaia in Europe was based on two specimens from the Rabejac Formation, now kept in the Museum National d'Histoire Naturelle Paris, nicely illustrated by Doubinger and Heyler (1975, Pl. 1, figs 13). The first specimen consists of two fragments of pinnae 12 and 15 cm long, lying side by side, and interpreted as one portion of a bifurcate frond just distal to the fork. The pinnules are elongated, up to 53 mm long and 7 to 9 mm wide, of alethopteroid-type with decurrent and confluent bases. The second specimen (Fig. 3B) shows excellent preservation of the pinnules with fine venation. There is also evidence that the pinnule laminae do not overlap and the pinnules do not show the pronounced biconvex ("roof shape") morphology described above in cf. Supaia ("Callipteris cf. uralensis") (Fig. 3A).
A dozen of other specimens, kept in the collections of Lodeve and Montpellier, can also be attributed to the genus Supaia. Two specimens correspond to nearly complete fronds showing a primary rachis bifurcating, at an angle of about 30[degrees], into two pinnae rachises 20 to 26 cm long. This suggests that the entire fronds were up to 34 cm long and about 15 cm wide (Fig.4). Pinnules were borne along the rachises and as well as shortly below the bifurcation of the rachis. Even if pinnules are partly hidden in the sediment their gross morphology is the same as in the Supaia specimen (Fig. 3B) originally illustrated by Doubinger and Heyler (1975). There is no evidence of a marked asymmetry in the size of the pinnules borne on the exterior and on the interior of the forked rachises. In some specimens completely preserved pinnules are up to 75 mm long and 12 mm wide, exceeding the values given by Doubinger and Heyler (1975). Therefore, pinnules are typically elongate, with a large length/width ratio (generally above 6) and they are generally positioned subopposite and densely spaced along the rachis (at intervals of 8 to 15 mm). We agree with previous authors who compared the Lodeve Supaia with the American species S. thinnfeldioides. Comparison with the illustrations provided by White (1929) shows that, amongst the six American species, S. thinnfeldioides is the most similar with regard to the size and morphology of the pinnules, differing mainly in pinnule spacing. Supaia has been recently described from the Permian of China (Wang, 1997) and Spain (Gand et al., 1997) but in both cases the pinnule morphology (and ratio pinnule length/width) was different and the fronds were significantly smaller than in the specimens from Lodeve. Additional information is needed about pinnule nervation and frond variability before a systematic decision is made concerning the Lodeve specimens which are designated provisionally as Supaia sp. aff. thinnfeldioides.
[FIGURE 3 OMITTED]
[FIGURE 4 OMITTED]
One specimen (Fig. 5A) in the Montpellier collections comes from the Rabejac Formation; it corresponds to a fragment of distorted leaf, being more than 15 cm long, but neither the base nor the top are preserved. The leaf is characterized by a prominent straight midrib, 6 (basally) to 4-5 mm thick, surrounded by lamina with parallel veins. The maximum width of the lamina, in the supposed median region of the leaf, is 60 mm but there is an apparent gradual diminution towards the basal region. The surface of the midrib is either smooth or longitudinally striated. Secondary veins appear to dichotomize at their very base, then they maintain an angle of 70-80[degrees] throughout the lamina; they are about 12 to 15 veins per cm at the leaf margin. There is no evidence of marginal dentation. The identification of this leaf is difficult due to incomplete preservation. We suggest similarities with Taeniopteris multinervia and T. fallax. The two species possess a strong midrib and a comparably broad lamina. However, some T. multinervia have been shown to possess marginal dentation and transferred to the species T. doubingeri Remy and Remy (1975). T. fallax is interpreted by Doubinger (1956) as spatulate-shaped instead of fusiform as suggested by the present specimen. Another difference concerns the vein density which is at least twice lower in the present specimen than in T. doubingeri, T. multinervia and T. fallax.
[FIGURE 5 OMITTED]
Taeniopteris sp. 2
A nicely preserved leaf, 17 cm long, with its intact apical region (Fig. 5B) is kept in the Lodeve Museum Collections. It is interpreted as the median and upper half of an originally very elongated-lanceolate leaf. The main difference with the specimen described above (Fig. 5A) concerns the narrow and rather indistinct midrib from which veins depart at an angle of 70 to 80[degrees] (Fig. 5C). Gentle undulations of the lamina have been preserved suggesting a rather quick taphonomic process. The maximum width of the lamina is of 60 to 70 mm, the vein density is of 14 to 17 veins per cm and there is no evidence of marginal dentations, all these features are similar to those of our first specimen. Due to its narrow midrib combined with a broad lamina, this specimen could be attributed to the species T. abnormis, a species sometimes considered as a synonym of T. multinervia (see discussion in Doubinger, 1956). Unfortunately, the origin of this specimen is not known.
[FIGURE 6 OMITTED]
It is interesting to note that the three species mentioned above (T. fallax, T. multinervia and T. abnormis) have been recorded by Doubinger (1956) from the Tuilieres flora of the Usclas-Saint Privat Formation of the same basin. However, it is the first time that Taeniopteris is recorded from red sediments, and the genus occurs up into the Rabejac Formation.
4.1.5. Cordaites and Conifers
Doubinger and Kruseman (1965) mentioned the frequency of very fragmentary remains of walchian conifers occurring both in the Rabejac Formation and in the underlying Transition Zone but only a few specimens have been illustrated and/or identified at the specific level (Table 1): Otovicia hypnoides (only from the Transition Zone), Ernestiodendron filiciforme and Culmitzschia hirmeri (both from the Transition Zone and the Rabejac Formation). Revision of the available collections provided little new data except one specimen from Rabejac, collected by J. Garric, showing a branched twig, about 12 mm diameter, with short and broad leaves (Fig. 6A). Morphologically these leaves appear succulent and resembling mesozoic conifers like Pagiophyllum or Cyparissidium. It is of particular interest, that this twig is associated with an isolated lanceolate leaf or bract of about 5 cm long and 2.5 cm wide, with a broad base, a sharp apex and a dense system of parallel veins (Fig. 6B). This is comparable to scaly leaves attributed to the cordaitean genera Crassinervia or Lepeophyllum (Neuburg 1965) from the Permian of Angara. A second specimen from Rabejac suggests the attachment of two similar scaly leaves to an axis.
5. Macroflora from the Salagou Formation
We present here, for the first time, information on plants from the Salagou Formation thanks to the intensive collecting of J. Lapeyrie in diverse fossiliferous rills and of additional collections of J. Schneider and colleagues from the Arieges and La Lieude localities (see suggested stratigraphy of these horizons in Garric, 2001).
During an excavation at La Lieude locality (site F 17 G) the red pelites have yielded a number of small stems partially preserved three-dimensionally but without anatomy, up to 30 cm long, with a diameter of 1 to 5 cm. These fragments cannot be identified but they may be interpreted as branches of woody plants. In association with these axes, a large number of almond-like organs (Fig. 6C) have been found; they range from 4 to 7 cm long and 2 to 4 cm wide and their surface is always striated. These problematic fossils are very difficult to interpret and their exact nature (? plants or invertebrates) is questioned. If they were plants, they certainly were deciduous organs (? seeds or buds of scaly leaves). It may be interesting to compare them to the possible cordaitean scaly leaves described above (Fig. 6B) from the Rabejac Formation which show a similar morphology.
The red pelites from the Arieges locality have yielded small repeatedly branched axes (2 mm diameter), terminating in narrow ultimate segments up to 40 mm long with a central vascular strand (Fig. 7A). They are interpreted as portions of fronds where the laminae are dichotomously or pinnate dichotomously divided as described in Dichophyllum moorei (Andrews, 1941, figs. 11-18; Meyen, 1987, fig. 48f).
The fossiliferous rills of the Salagou Formation have been discovered by J. Lapeyrie, in which he found new well preserved fossils (mainly crustaceoans and insects). These rills are silt bodies formed of fine siltites with a colour varying from grey-green to red; some fossils plants have been found in association with, but less commonly than, animals. Among the plants are cylindrical axes (Fig. 7B), certainly fragments of woody branches, that cannot be identified, as well as twigs with attached incomplete linear leaves (Fig. 6D, arrow) that may represent voltzialean conifers. Of more interest is a small cone 1.6 mm diameter, three-dimensionally preserved but exposed in median longitudinal section (Fig. 7D). It is interpreted as a male cone composed of peltate microsporophylls, the elongate sporangia being attached to the heel of the microsporophyll and parallel to the stalk. Pollen sacs are visible near the top of the cone and one is lying obliquely (arrows, Fig. 7E). This pollen cone is similar in size and organization to Triassic cones referred to as Masculostrobus or Willsiostrobus (Grauvogel- Stamm and Schaarschmidt, 1978, 1979). Several examples of narrow, dichotomously branched axes have been found in fossiliferous rills (Fig. 7C). They are reminiscent of leaves ofSphenobaiera digitata (Meyen 1987, fig. 48h) or even of the Mesozoic genus Czekanowskia (Florin, 1936, Pl. 32, figs 7-10). Finally, one small taeniopterid-like leaf (Fig. 5D), only 7 mm wide, is considerably smaller than the taeniopterids from the Rabejac Formation; however, the well-marked main vein and branched lateral veins are well preserved and this specimen certainly belonged to a pinnate taeniopterid leaf with narrow pinnules like Taeniopteris coriacea.
The present reinvestigation of the fossil plant assemblages from the Permian red beds of the Lodeve Basin revealed a marked decrease in plant diversity by comparison with the older flora from the "grey Autunian" which comprises 46 taxa (Doubinger, 1956). In the Tuilieres-Loiras Formation, 22 taxa have been recorded, including those from the Transition Zone, with 18 taxa found in grey sediments (Doubinger, 1963; Galtier and Broutin, 1995) and only 8 in red sediments (Doubinger and Kruseman 1965). For the overlying Viala Formation, which yielded a microflora (association LO3 of Doubinger et al., 1987), we found a single specimen that we identified as Rhachiphyllum sp. However the Rabejac Formation yielded a dozen of taxa whilst only a pair of specimens were identifiable from the Salagou Formation. The unfavourable conditions of fossilisation in these red sediments evidently account for the small number of well preserved and taxonomically identifiable specimens.
[FIGURE 7 OMITTED]
According to previous work by Doubinger and collaborators and to the present investigation, we propose the following lists of plant assemblages from the successive red beds in the Lodeve Basin. (N.B. The taxa inside brackets have not been found again or never illustrated and they are considered as very doubtful):
1) Red beds from the Transition Zone (Tuilieres --Loiras Formation): Autunia conferta, cf. Supaia = "Callipteris cf. uralensis", cf. Peltaspermum martinsii, Walchia sp., Culmitzchia cf. hirmeri, Otovicia hypnoides, (Schuetzia sp., cf. Ullmannia)
2) Viala Formation: Rhachiphyllum sp.
3) Rabejac Formation: Autunia conferta, Rhachiphyllum sp., cf. Peltaspermum martinsii, cf. Supaia ="Callipteris cf. uralensis", Supaia sp. aff. thinnfeldioides, Taeniopteris sp.1 et sp. 2, cf. Lepeophyllum, Walchia sp., Culmitzchia cf. hirmeri, Ernestiodendron filiciforme, Pagiophyllum-like leafy twigs, (Pecopteris cyathea, cf. Pseudoctenis middrigensis).
4) Salagou Formation: cf. Willsiostrobus, Taeniopteris sp. aff. coriacea, Sphenobaiera sp., Dichophyllum aff. moorei (? n. sp), diverse leafy conifer twigs and small branched axes, probable seeds and roots, all taxonomically unidentifiable even at the generic level.
Some remarks have to be made concerning these lists of plant assemblages:
- We only took in consideration the specimens with an undisputable mention of origin, this means that several ten specimens in the collections of Montpellier and Lodeve have been identified but not listed, they all correspond to known taxa.
- In the list of plants from the Transition Zone, we are very sceptical with regard to Schuetzia and Ullmannia, two taxa not illustrated and just mentioned with strong reservations by Doubinger and Kruseman (1965).
- Similarly in the Rabejac list, the unique specimen attributed to Pseudoctenis has not been located and the short description provided by Doubinger and Kruseman could apply to many specimens of "Callipteris cf. uralensis"= cf. Supaia. We are also sceptical with regard to the identification of Pecopteris cyathea, of which the figured specimen could not be located.
The comparison of the floras from the red beds with those from the grey sediments reveals differences that are certainly ecologically significant; this is particularly evident if we consider the probably contemporaneous floras from the grey versus the red beds of the Transition zone. The sphenopsids (Annularia spicata, Calamites cistii, C. cruciatus, C. gigas, Sphenophyllum thonii) are very diversified in the first but absent in the red sediments; similarly the callipterids with small pinnules (Arnhardtia mouretii, Gracilopteris strigosa, Rhachiphyllum schenkii), but also Odontopteris subcrenulata, Cordaites borassifolius and Poacordaites which were extending from the basal Autunian into the grey sediments of the Transition zone become absent in the red sediments. The changes in environment (increased dryness) which were certainly responsible for these differences, did not affect the conifers and some callipterids so abruptly; Autunia conferta seems to persist up to the Rabejac Formation whilst callipterids (Supaia) with large and thick pinnules were certainly better adapted to the dry environment. Interestingly also, some broad-laminate taxa like Taeniopteris, already present in Late Carboniferous coal swamp environment and in the basal "Autunian", reappear in the Rabejac Formation and apparently extend up into the Salagou Formation. Some new data, for example the possible occurrence of cordaiteans with scaly leaves of Lepeophyllum or Crassinervia type, previously known from the Permian of Angara, the occurrence of Dichophyllum-like leaves and the conifers with broad, possibly succulent, leaves and small cones of Willsiostrobus type similar to Triassic conifers, may represent new transitional forms to the Mesozoic flora. This needs to be confirmed by additional collecting and observations.
7. Comparison with other contemporaneous floras and conclusions
Considering the plant species diversity in the "red beds" of the Transition zone and the Rabejac Formation, the Lodeve Basin must be considered as the second in taxa richness after the Hermit Shale (Grand Canyon, Colorado, USA) with regard to this type of facies. This is particularly spectacular concerning the abundance of fronds belonging to Supaia, a genus only known, except the Hermit Shales, in Shanxi, China and in the Cantabrian Mountains, Spain. Therefore one may suggest that these localities (at least the euramerican ones) are approximately contemporaneous. In fact, a correlation of the Pena Segra locality (Cantabrian mountains) with the "zone 4" of the Rajejac Formation has been already proposed (Gand et al., 1997) based on ichnofossil biozones.
In contrast, it is more difficult to compare the flora from the Salagou Formation with those from "red beds" of other west-European Permian Basins. Most of the red beds of other Basins such as Rodez, Saint-Affrique, or the Upper Rotliegendes Thuringia, are generally "aphytic" or contain plant associations comparable to that of Rabejac, even in the upper levels of the series: for example Gasberg locality, Rotterode beds, in Thuringia (Lutzner, 1987).
The famous "thuringian" macrofloras reported in other basins such as Agay (Visscher, 1968), Toulon (Durand, 2006), etc., with Ullmannia frumentaria, U. bronnii, Quadrocladus orobiformis, Pseudovoltzia liebeana, Sphenobaiera digitata come from dark grey sediments, rich in organic matter (a facies that does not occur in Lodeve-Saint-Affrique-Rodez), intercalated within the red beds deposits. However we found, in the Salagou Formation, some leafy twigs similar to Ullmannia or Pseudovoltzia liebeana, with rare cones suggestive of conifers known in the Triassic.
Comparisons of macrofloras and, a fortiori, biostratigraphic correlations, between the red beds of the different west European Permian basins remains difficult. An exhaustive re-investigation of the collections of specimens originating from the different localities and, eventually, new collecting in this "unpromising" facies, supposed late Permian ("Thuringian" s.l.) would be necessary for comparison with the Salagou paleoflora and for establishing an inter-calibration with the zonation based on ichnofossils.
We are greatly indebted to J. Lapeyrie, J. Garric, J. Schneider, G. Gand, P. Ellenberger and D. Heyler who collected a number of specimens used in this study. We thank also J. Dejax and D. de Franceschi, Museum National Histoire Naturelle, Paris and M. Valles-Bled and S. Fouche, Musee Fleury, Lodeve, for access to material kept in their Museum collections.
Received: 18/02/07/ Accepted: 12/08/07
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J. Galtier (1), J. Broutin (2)
(1) AMAP, UMR 5120 CNRS, CIRAD, TA A-51/PS2, Boulevard de la Lironde, 34398 Montpellier Cedex 05, France e-mail: email@example.com
(2) UMR CNRS 5143 Paleobiodiversite et paleoenvironnements, Paleobotanique - Paleoecologie /Paleodiversite, Systematique et Evolution des Embryophytes, Universite Paris 6, case courrier 1201, 12 rue Cuvier, 75005 Paris, France
Table 1.--Plants known from red beds of the Transition Zone and of the Rabejac Formation according to previous studies by Doubinger and Heyler 1959 (=DH1959), Doubinger and Kruseman 1965 (=DK 1965) and Doubinger and Heyler 1975 (=DH1975). Table 1.--Plantas conocidas de la Zona de Transicion de la Formacion Rabejac segun los estudios previos de Doubinger y Heyler (1959) (=DH1959), Doubinger y Kruseman (1965) (=DK1965) and Doubinger and Heyler (1975) (=DH1975). Red beds of the Previous data Transition zone Pecopteris cyathea P. cyathea var. major Callipteris conferta DK 1965, pl.12, fig. 2 Callipteris uralensis C. cf. uralensis DK 1965, pl.12, fig. 4 Callipteris martinsii DK 1965 not figured Schuetzia sp. DK 1965 not figured cf. Pseudoctenis middrigensis Supaia sp. Walchia sp. DK 1965, pl. 13, fig.3 Culmitzchia cf. DK 1965, pl. 13, fig.4 hirmeri Ernestiodendron filiciforme cf. Ullmannia DK 1965 not figured Previous data Rabeiac Formation Pecopteris cyathea DK 1965, pl. 12, fig. 3 P. cyathea var. major DK 1965 not figured Callipteris conferta DK 1965, pl.12, fig.1 Callipteris uralensis DH 1959, pl. 15, figs 1-3 C. cf. uralensis DK 1965, pl.12, fig. 5 Callipteris martinsii DK 1965, pl.13, figs 1,5 Schuetzia sp. cf. Pseudoctenis DK 1965 not figured middrigensis Supaia sp. DH 1975, pl.1, figs 1-3 And new data Walchia sp. DK 1965 not figured Culmitzchia cf. DK 1965 not figured hirmeri Ernestiodendron DK 1965 not figured filiciforme cf. Ullmannia New data Proposed list for the Previous data Rabejac Formation Pecopteris cyathea ? Pecopteris cyathea P. cyathea var. major Callipteris conferta Autunia conferta Rhachiphyllum sp. Callipteris uralensis cf. Supaia C. cf. uralensis Callipteris martinsii cf. Peltaspermum martinsii Schuetzia sp. cf. Pseudoctenis cf. Pseudoctenis middrigensis middrigensis Supaia sp. Supaia sp. aff. thinnfeldioides Walchia sp. Walchia sp Culmitzchia cf. Culmitzchia hirmeri cf. hirmeri Ernestiodendron Ernestiodendron filiciforme filiciforme cf. Ullmannia ? Calamites Taeniopteris sp. 1,2 cf. Lepeophyllum cf. Pagiophyllum
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|Author:||Galtier, J.; Broutin, J.|
|Publication:||Journal of Iberian Geology|
|Date:||Jan 1, 2008|
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